1. Field of the Invention
The present invention relates to an image coding technology, and it particularly relates to method and apparatus for performing arithmetic coding on image data.
2. Description of the Related Art
In the twentieth century, which was often called “The Century of Images”, a great variety of pictures and images were produced and put to use in movies, television broadcasts and so forth. During the 1990's in particular, the widespread use of PCs (personal computers) and other information equipment, the popularization of digital cameras, color printers and so forth and the explosive increase in the use of the Internet accounted for deep infiltration of the culture of digital images into everyday life of ordinary people. Under these circumstances, coding and compression technologies, such as JPEG (Joint Photographic Expert Group) for static images and MPEG (Motion Picture Expert Group) for moving images, have been standardized so as to improve the facility of distribution and reproduction of the images through recording media, such as CD-ROMs, and transmission media, such as networks and broadcasting waves.
As demand for higher image quality grew and related technologies advanced to meet it, there have also been growing needs for new coding technologies. It has been some time since the work on JPEG2000, which is an advanced version in the JPEG series, was initiated, and as a result the specifications have been standardized and their practical applications have started.
The coding algorithm of JPEG2000 not only involves complex processing, such as wavelet transform and bit-plane entropy coding, but also places heavy loads on the CPU and uses much memory capacity. Thus, a strategic design policy is required if the specifications of JPEG2000 are to be realized efficiently.
A naive design of a coding algorithm in accordance with the specifications may produce a hardware structure overloading the CPU, too large a memory capacity required or other problems. Particularly when it is to be mounted on small electronic devices, such as digital cameras or portable telephones, which are subject to limitations on battery capacity, some ingenious schemes are required to hold down power consumption and memory capacity at a low level.